Devices for spraying liquids or liquid-gas mixtures for various purposes such as applying paint, insecticide, herbicide, water, fertilizer solutions and cleaning solutions exist in the prior art; indeed, several of these devices have been the subject matter of United States Patents and various configurations of such devices have been disclosed. In general terms, the fundamental objective of each such apparatus has been similar: To direct a pressurized gas through a conduit which conduit is in communication with a source of liquid to be sprayed, to draw upon the liquid, convert it to a spray or mist (i.e., atomize it) and discharge it from the liquid source onto a surface or into the air some distance from the liquid source. The differences among these spraying devices have primarily resided in the mechanisms employed to achieve the objective. Some of these prior mechanical arrangements have resulted in devices which spray in successive, finite bursts while others rely on a continuous flow of gas to discharge atomized liquid in an essentially continuous flow. Five patented devices relevant to the instant invention are briefly discussed below.
U.S. Pat. No. 1,822,553 issued to L. P. Uphoff et al. in 1928 discloses a spraying device which has a container for paint to be sprayed with a tube extending from the top of the container where it terminates in a nozzle. Movable into and out of perpendicular alignment with the paint tube is an air (gas) tube terminating in a nozzle which air tube is connected to a supply of air under pressure for expulsion through the nozzle. The device is directed toward paint spraying and is therefore dependent upon a continuous flow of gas through the air tube to deliver an even amount of paint to the surface being painted.
U.S. Pat. No. 2,127,189 to Scullari discloses one example of a single-burst spraying device wherein the squeezing action of a user's hand is directly responsible for the compression and ejection of a burst of gas under pressure through a port and over a liquid conduit which is in communication with the container storing the liquid to be sprayed. Specifically, the user's squeezing of a trigger moves a piston inside a gas cylinder to compress gas in the cylinder between the piston and a partition to force the gas through a hole in the partition and over the open end of the liquid conduit. When the user releases the trigger, the trigger is drawn back to an at-rest position by a spring and is ready to be squeezed again for the discharge of another finite burst of gas.
U.S. Pat. No. 2,264,312 discloses a spraying device which depends on a continuous flow of gas to produce a continuous spray of finely divided liquid particles.
U.S. Pat. No. 2,635,921 recites in every claim for the device described therein a "cartridge of self-pressurizing fluid propellant." Specifically, the invention relies on a prepackaged, disposable container of pressurized gas which is then mounted to the device and punctured by a piercing tool on the body of the sprayer itself allowing the gas in the cartridge to come into communication with a regulator assembly for controlled discharges of gas therefrom. This device is capable of producing both short, finite bursts or longer, more continuous discharges of gas and liquid depending on the length of time the user depresses the trigger.
Like the invention of U.S. Pat. No. 2,127,189 to Scullari, the invention disclosed in U.S. Pat. No. 4,477,023 to Gates relies upon the user's squeezing of a trigger to pressurize and discharge gas through a port in finite bursts whereinafter a spring returns the trigger to its at-rest position and awaits subsequent activation by the user.
Of the devices described, the ones relating to continuous gas flow are less relevant to the present invention than those that discharge individual, finite bursts of gas and spray; the instant invention is generally of the latter type in that it produces single, finite bursts of gas and gas/liquid mixture. However, the mechanisms employed in the present invention for producing gas/liquid spray are substantially different from those employed in the two patented devices described above that produce finite bursts, namely, those of U.S. Pat. No. 2,127,189 to Scullari et al. and U.S. Pat. No. 4,477,023 to Gates, and yield corresponding advantages over these two devices. As previously described, the user of the Scullari and Gates devices must squeeze a trigger to translate a piston within a cylinder to pump gas through an exit port under pressure; in both instances gas is ejected for the duration of the user's squeezing action. If the user squeezes slowly, the gas discharge will be of a longer duration at a lower pressure within the gas chamber than if the user squeezes the trigger rapidly. There are two problems inherent in both prior designs. First, the user cannot reliably duplicate the rate at which he or she squeezes the trigger in order to regularly produce bursts of substantially equivalent duration, pressure and quantity. Second, in those applications where aim is important for spraying a particular region on a surface, the aim of the user is interfered with throughout the pulling of the trigger. This deviation in aim increases as a function of the force imparted to the trigger by the user. This principle is analogous to the proposition that it is generally easier to hit a target with the bullet from a handgun when the trigger is a "hair-trigger" as opposed to a trigger requiring substantial force over a substantial distance to discharge the gun.
The instant invention alleviates both difficulties discussed above and provides further advantages and objectives which are stated explicitly below or will be implicit to a user.